[gentoo-dev] Changes in toolchain.eclass to enable Ada

[Alfredo Tupone]

I would like to revive the Ada support in gentoo.

One ada compiler is produced by AdaCore and is provided in three
versions, in the order starting from the best supported :

1) GnatPro, available with a contract support.

2) Gnat-GPL that can only build GPL-3 product

3) The gnat included in the gcc tree that is GPL-3 with exception.

Gnat-GPL is very like the gnat in the gcc-tree so it can be built in
the same way of sys-devel/gcc

To be compiled from source the gcc compiler needs a C, C++, and Ada
Compiler. I will provide one with the gnat-gpl-bin tar that could be
installed under /opt . When the gcc is properly compiled we don't need
it any more.

I would like to start including, in the gentoo tree, GNAT-GPL
built in the same way as sys-devel-gcc and selectable with gcc-config

As for instance gnat-gpl-2014 is based on gcc-4.7.4 they cannot coexist
and gnat-gpl-2014 will block sys-devel/gcc-4.7.4

As a reference I have my overlay on https://github.com/atupone/overlay
and a pull request at https://github.com/gentoo/gentoo/pull/3186

To start I need to change the toolchain.eclass 

-	tc_version_is_at_least 4.7 && IUSE+=" go"
+	tc_version_is_at_least 4.7 && IUSE+=" go ada"

-	# We do NOT want 'ADA support' in here!
-	# is_ada && GCC_LANG+=",ada"
+	# We do want 'ADA support' here!
+	is_ada && GCC_LANG+=",ada" 

-	for x in cpp gcc g++ c++ gcov g77 gcj gcjh gfortran gccgo ; do
+	for x in cpp gcc g++ c++ gcov g77 gcj gcjh gfortran gccgo gnatbind; do 

Thats all for that.

Then, to not change the behaviour of the gcc-compiler, we could mask the
ada use flag for sys-devel/gcc, at least temporarily

---------------------

I would like to have comments on that, particularly because:
a) it is going to add a use flag to sys-devel/gcc that will bring gcc
to be rebuilt on most system, 
b) the gnat-gpl, if selected with gcc-config, can be used to recompile
all the system, and maybe is not so good ?

Alfredo